Fix/aiokafka tests fixes

[dorlib]

Description

Fix two pre-existing test warnings in the aiokafka instrumentation test suite:

1. Unclosed AIOKafkaProducer in test_send_and_wait, the test creates a producer via producer_factory() but never closes it. Fixed by wrapping the test body in try/finally and calling await producer.stop().

2. RuntimeWarning: coroutine was never awaited in test_wrap_getmany, the _create_consumer_span mock was declared as mock.MagicMock but the real function is async. The return value's method calls produced unawaited coroutines. Fixed by changing the type hint to mock.AsyncMock.

Fixes #4383

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• tox -e py3-test-instrumentation-aiokafka all 17 tests pass
• Verified Unclosed AIOKafkaProducer warning no longer appears
• Verified RuntimeWarning: coroutine was never awaited no longer appears during test execution
• Ran with -W error::RuntimeWarning all 17 tests still pass

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[tammy-baylis-swi]

Thanks again @dorlib ! Runs like this one are quieter.

Please could you do a tox -e precommit for some formatting fixes.